Or do what I did and have a Physician on board.
Seriously though, she says that prior to a "world cruise" she would have a defibrulator onboard for sure. I have advanced first aid and CPR, and she says that would be a bare minimum in terms of training for every crewmember. Doing it in a "self taught" manner is better than nothing, but won't give you the same knowledge that you can obtain in a class with demonstrations by instructors. To be really safe as you're making long passages, etc., a well equipped medical supply kit along with a good reliable communications system can put you in touch with a knowledgable practioner who can guide you in the event of an extreme emergency. An EPIRB could be necessary to save life and hopefully that leg in some extreme circumstances. All this must be balanced upon the amount of time and money you want to spend for training. There's no doubt that EMT or "wilderness first aid" or any number of advanced courses can't hurt.
Fair winds & best of luck to you